We all see and use lifts and elevators on a regular basis, but how many of us know how they really work? Not many, which is not surprising given that there are few lifts where you can actually see the components in operation. Usually the only parts of the lift you see are the call button and the the interior of the car. Occasionally you might come across a glass life where the elements are exposed, and you can actually see the various components in operation as the lift is used. Some types of lift such as external platform lifts sometimes have more of their mechanisms on show, as of course being outside there is less building to hide the workings behind.
There are two basic passenger carrying lift designs: hydraulic lifts and roped lifts. Hydraulic lifts operate by means of a hydraulic ram underneath the car which raises and lowers the lift via a piston. A motorised pump forces fluid from a tank located outside of the lift shaft into the piston which elevates the car, shutting off at a predetermined point allowing the car to be held at each floor level for entry and exit of passengers. For the lift to descend the motor simply has to allow the release of a measured amount of the fluid and a slow, smooth rate. Hydraulic lifts are normally used up to 5 to 8 floors and can have a typical speed of 100-200 feet per minute.
Roped lifts, otherwise known as cable borne elevators (the most common ones in films requiring mild peril and escape scenarios) are commonly thought to be the most popular elevator design available. Instead of being pushed and pulled from underneath as in the case of hydraulic lifts, the roped lift is lifted and lowered by means of a series of cables located above the car. Steel ropes operate over a pulley which grips the ropes. An electric motor operates the pulley, and as it is operated, so is the pulley and ropes. The ropes are also connected to a counter weight to help conserve energy. Despite my film analogy it is thought that there have been no recorded cases of elevators free falling as is often seen on screen.
Specialised lifts such as hydraulic lifts for disabled access are often tailored to the building in which they are situated, and can usually hold 1 to 5 people, depending on their design. Wheelchair lifts will normally carry just one person at a time, including stairisers which platform lifts which run up the side of staircases where an actual elevator is impractical such as in listed or otherwise awkward buildings.